1. Field of the Invention
The invention relates to a pump having a housing in which an electric motor of a pump stage driven by a shaft of the electric motor is arranged.
2. Description of the Prior Art
Such pumps are known and are used in motor vehicles for conveying additives added to the fuel. The added additives are intended to reduce nitrogen oxides in the exhaust gas of motor vehicles. As a result of the chemical reaction, which is brought about thereby, these pumps are also known as SCR pumps. The additive is supplied by the SCR pump from a container via a line to the fuel. To prevent freezing of the line that contains the additive, the line is emptied outside travel operation. The emptying is carried out by reversing the polarity of the rotation direction of the SCR pump so that the conveying direction of the SCR pump is directed from the line into the additive container. Positive-displacement pumps are used since these can convey in both a forward and backward direction depending on the rotation direction. The disadvantage of positive-displacement pumps is their more complex construction is consequently more cost-intensive.